1. Technical Field
The present disclosure relates to an apparatus for sensing a spin chuck for a spin coating unit, and more specifically, to an apparatus for sensing a spin chuck for a spin coating unit which enables an operator to directly confirm whether or not a spin chuck has been assembled normally in the course of assembling.
2. Discussion of Related Art
Generally, the fabrication of a semiconductor device includes the forming of a semiconductor circuit on a wafer. For example, the forming of the semiconductor circuit is performed using growth and deposition of a thin film, coating of a photoresist, etching, implanting, and the like by means of a photo-stepper, an implanter and the like. The procedure is then repeated to form desired circuits.
In the procedure for fabricating a semiconductor device, the process equipment for performing a series of processes including a coating process for coating the photoresist and a developing process for developing the coated photoresist is generally referred to as a spinner or spinner equipment.
The spinner equipment is composed of an adhesion unit for a pretreatment process a spin coating unit which coats photoresist on a wafer at a predetermined thickness with a centrifugal force a baking unit which cures the coated photoresist, a cooling unit which cools down the baked wafer, a stepper which exposes the wafer coated with the photoresist to light, and a developing unit which develops the exposed wafer.
The spin coating unit of the spinner equipment rotates a wafer and discharges a photoresist onto the top face of the rotating wafer to uniformly coat the wafer with the photoresist which is spread onto the surface of the wafer with a centrifugal force.
This spin coating unit is provided with a spin chuck to firmly fix a wafer, and a wafer is sucked and firmly fixed to the spin chuck by vacuum pressure.
Moreover, the spin chuck is designed to be rotatable at constant speed and is covered with an outer case called a bowl so that, during spin coating, the surplus photoresist which remains after being coated on a wafer placed on the spin chuck may be collected into the bottom of the bowl and then drained to the outside. In this spin coating unit, a wafer is loaded/unloaded by elevation of the spin chuck or the bowl.
Further, a wafer is transferred by a transfer robot provided outside the bowl.
In addition, the spin coating unit is adapted to regularly or irregularly perform a checkup and a cleaning of the equipment. In this case, some constituent parts of the equipment are disassembled, cleaned and reassembled.
Among the constituent parts of the equipment which are disassembled as such, the spin chuck is separated from a shaft guide, cleaned, and reassembled.
In this case, the spin chuck is configured such that a chuck plate that is a flat plate on which a wafer is to be placed and a tubular stationary shaft having a predetermined height and provided on the bottom center of the chuck plate are integrally provided.
Accordingly, the spin chuck is tightly fitted to a rotary shaft provided within the shaft guide while the stationary shaft of the spin chuck is inserted into the shaft guide having a larger inner diameter than the outer diameter of the stationary shaft.
Meanwhile, the spin chuck can be manipulated by a user, for example, an engineer from the rotary shaft.
For example, the spin chuck is manually separated from the rotary shaft for checkup and cleaning of the equipment, and manually reassembled when the cleaning is finished.
However, once the spin chuck is separated from the rotary shaft and then reassembled thereto the spin chuck may not always be assembled to the rotary shaft normally due to, for example, an engineer's mistake.
If the spin chuck is not assembled exactly or precisely as such, a wafer which generally is loaded/unloaded from one side of the spin chuck may cause difficulties in that it may collide against the spin chuck while being transferred by a blade of a transfer robot
As the vertically spaced clearance between the spin chuck and the blade of the transfer robot or a wafer to be transferred by the blade is extremely low, the wafer may be broken due to collision of the blade or wafer against the spin chuck during loading/unloading of the wafer if the spin chuck is not normally assembled to the rotary shaft or a process error may occur which may cause the breakage of parts.
In particular, as the occurrence of such a process error may cause the operational stoppage of the equipment, the productivity of equipment may also thereby be decreased.